The present invention is directed to a computer system and a computer monitor. More particularly, the present invention is directed to an extender for transmitting an enhanced video signal and increasing the distance between a computer system and a computer monitor.
Computer systems typically include a computer graphics controller or some other graphics or video generator that outputs analog red, green and blue (xe2x80x9cRGBxe2x80x9d) video signals. The RGB signals are sent to a computer monitor where they are displayed. The cable coupling the RGB signals to the computer monitor from a computer system requires three separate wires, one for each RGB signal. Further, an additional two wires are sometimes required for horizontal and vertical synchronization signals.
There may be a need to extend the distance between a computer system and a computer monitor. For example, it may be desirable to have the computer system in one room and the computer monitor in another room. One known way of accomplishing this is to have three RGB wires and two horizontal and vertical synchronization wires extending between the rooms. However, extending five separate wires can be costly and difficult, especially if more than one room requires a monitor.
Another known way of extending the distance between a computer system and computer monitor is to encode the RGB signal into a single National Television Standards Committee (xe2x80x9cNTSCxe2x80x9d) composite television signal using a YUV color space format. The television signal can be transmitted, for example, in a known manner on a coaxial cable. Thus, only one extended wire needs to be installed between the computer system and computer monitor. However, when an NTSC YUV signal is decoded back into an RGB signal for display on a computer monitor, the color quality and sharpness of the resultant RGB image is substantially lower than the original RGB image.
Based on the foregoing, there is a need for a method and apparatus for more easily transmitting an RGB signal over an extended distance while maintaining the quality of the signal.
One embodiment of the present invention is an extender that transmits red, blue and green signals, and vertical and horizontal sync signals. The extender generates a subcarrier reference frequency signal from the vertical and horizontal sync signals and combines the subcarrier reference frequency signal with the vertical and horizontal sync signals and the green signal to generate a green portion. The extender then quadrature amplitude modulates the blue signal and the red signal by the subcarrier reference frequency signal to generate a color portion, and combines the green portion and the color portion to generate an enhanced video signal.